1. Field of the Invention
This invention relates generally to electrical outlets, and more specifically to an improved safety feature to protect against injury caused by metal objects other than plugs being inserted into the openings of the electrical outlets.
2. Description of the Related Art
Electrical outlets have become standardized to the two-prong or three-prong configurations. The exposed face of these outlets have narrow openings that prevent even small children's fingers from coming in contact with dangerous electrical current. However, children sometimes do insert small metal objects, such as bobby pins and paper clips into the narrow openings of electrical outlets, occasionally with disastrous results.
A similar hazard is found in a partially inserted plug when used with the commonly used electrical outlet. Children's fingers, and even adult's fingers, can get across the prongs of a partially inserted plug, resulting in an electrical shock and/or burn. If the person has another part of his body in contact with an electrical ground, a serious injury or fatality could result.
It is known to provide a safety feature in electrical outlets to prevent electrical shock and injury. For example, U.S. Pat. No. 2,540,496 to J. J. Sperrazza, issued Feb. 6, 1951, discloses an electrical outlet having a non-conducting cam block located about half way down the length of each plug prong slot that forces together the contact points for the opposite side of the receptacle when a plug prong is inserted about half way into the electrical outlet. The outlet is thus made electrically hot while at least one half of the prongs of the plug being inserted are still exposed to contact by the person inserting the plug. This is required to prevent electrical arcing in the electrical outlet. Furthermore, the disclosure provides that inserting a plug into one outlet of a multi-outlet receptacle makes both outlets electrically hot even though one is not in use.
In U.S. Pat. No. 2,751,567 to C. H. Bissell et al, issued Jun. 19, 1956, is disclosed an explosion proof electrical connector system requiring a specialized electrical outlet and a specialized mating electrical plug. There is no teaching of how to utilized this invention with a conventional residential or commercial electrical outlet commonly used for lamps, small appliances, office equipment, and small power tools.
Another method of providing safety measures to the common electrical duplex outlet is disclosed in U.S. Pat. No. 3,669,285 to Leatherman, issued Oct. 17, 1972. The disclosure teaches using a specialized form of the ground prong on a three-prong plug to make the outlet electrically hot. The teaching will not work with the common polarized two-prong plug at all, and will only work with a three-prong plug have a special configuration. In addition, there is no teaching of how to prevent both outlets from becoming electrically hot when only one outlet has a plug inserted into it. Another teaching of using the ground prong of a three-prong plug to activate the outlet is disclosed in U.S. Pat. No. 3,755,635 to McGill, issued Aug. 28, 1973. In this teaching the ground prong activates a low-current microswitch, which in turn activates a relay allowing electrical current to flow to the plug. While not disclosed, the relay apparently is large enough to cause a standard duplex outlet to contain only one plug outlet. Again there is no teaching of how to use a polarized two-prong plug with this invention. In fact such a plug, common on most small appliances, will not work with this invention.
A safety duplex outlet for a polarized two-prong and three-prong plug is disclosed in U.S. Pat. No. 5,095,182 to Thompson, issued Mar. 10, 1992. This disclosure teaches the use of a microswitch mounted behind the large slot of a standard polarized wall outlet. However, a person inserting a wire, paper clip, or the like, of any width that fits within the outlet slots, into both slots could activate the microswitch located at the bottom of the slot and thereby circumvent the safety feature. In addition, the addition of microswitches mounted on the bottom of the outlet would prevent the mounting of the outlet in standard electrical boxes.
In U.S. Pat. No. 5,347,095 to Zeder, issued Sep. 13, 1994, is disclosed an electrical outlet which gives an audible warning when an electrical plug is removed from it. There is no teaching of how to provide an electrically safe outlet.
U.S. Pat. No. 5,513,999 to Fry et al, issued May 7, 1996, discloses a manner of activating an outlet/plug assembly upon partial insertion of the plug into the outlet. However, the outlet and plug are non-standard designs, which would require the replacement of both the common standard duplex outlet, and the commonly provided polarized two-prong and three-prong plugs.
Thus, there continues to be a need for an electrical outlet having an enhanced safety feature to protect against injury caused by inserting conductive objects, other than electrical plugs, into the outlet openings.